Many vibration-wave driving devices have been proposed, which excite a vibration in a vibrator and move a movable body pressed in contact with the vibrator.
Such vibration-wave driving devices are regarded as important functional components in optical apparatuses that are required to perform particularly precise operation. For example, there is a two-dimensional driving apparatus, which is used as an image-shake correcting apparatus, in which a plurality of linear vibration-wave driving devices (capable of linearly moving a movable body) are arranged to combine their driving operations to move the movable body in different directions in two-dimensional space (see PTL 1 and PTL 2).
However, when the driving operations of the vibration-wave driving devices are combined, the moving direction of the movable body and the driving direction of any of the vibration-wave driving devices may intersect at right angles or at substantially right angles, depending on, for example, the moving direction of the movable body.
In this case, the vibration-wave driving that intersects with the moving direction at right angles or at substantially right angles is unable to contribute to driving the movable body. Additionally, a frictional force produced by contact between the movable body and the vibration-wave driving device causes a load on movement of the movable body. This leads to an energy loss, and results in an output loss.
As a driving device other than the vibration-wave driving device, there is a non-contact driving device, such as a voice coil motor, which is capable of transmitting the displacement or driving force to a movable body without contact. It is possible to realize a two-dimensional driving apparatus in which a non-contact driving device and a vibration-wave driving device are arranged to have different driving directions so as to move a movable body in different directions in two-dimensional space.
However, when the non-contact driving device tries to drive the movable body, a frictional force produced by contact between the vibration-wave driving device and the movable body causes a load on movement of the movable body.
When a contact driving device which is not a vibration-wave driving device is used in combination with a vibration-wave driving device, a load on movement of the movable body also occurs.
This means that if, for example, the vibration-wave driving devices described above are used as driving devices for an image-shake correcting apparatus, the performance of the image-shake correcting apparatus may be degraded.
To address the problems described above, PTL 1 and PTL 2 propose techniques in which an output loss is reduced by exciting a vibration in the vibration-wave driving device in a pressure direction with respect to the movable body so as to reduce a frictional force.